Charging method for non-aqueous electrolyte secondary battery by repeating a set of constant current charge and constant voltage charge and battery pack implementing the charging method

A battery pack comprising:

• at least one non-aqueous electrolyte secondary battery;
• a charge circuit configured to receive an electric power from an outer power source, and to charge the secondary battery;
• and
• a control unit that controls charge of the secondary battery by the charge circuit, wherein:
• the control unit that controls the charge circuit such that the charge circuit charges the secondary battery by repeating f times a charging sequence of a constant current charge and a constant voltage charge, subsequent to the constant current charge, where f is an integer of 2 or more,
• an nth charging sequence comprises charging the secondary battery at a current Ic(n) until a voltage of the secondary battery increases to Ec(n), and subsequently charging the secondary battery at the voltage Ec(n) until the current decreases from Ic(n) to Ic(n+1), and
• an (n+1)th charging sequence comprises charging the secondary battery at the current Ic(n+1) until the voltage of the secondary battery increases to Ec(n+1), and subsequently charging the secondary battery at the voltage Ec(n+1) until the current decreases from Ic(n+1) to Ic(n+2),
• where n is an integer of 1 or more and f-1 or less.